A regulatory GhBPE-GhPRGL module maintains ray petal length in Gerbera hybrida

Abstract

The molecular mechanism regulating petal length in flowers is not well understood. Here we used transient transformation assays to confirm that GhPRGL (proline-rich and GASA-like)—a GASA (gibberellic acid [GA] stimulated in Arabidopsis) family gene—promotes the elongation of ray petals in gerbera (Gerbera hybrida). Yeast one-hybrid screening assay identified a bHLH transcription factor of the jasmonic acid (JA) signaling pathway, here named GhBPE (BIGPETAL), which binds to the GhPRGL promoter and represses its expression, resulting in a phenotype of shortened ray petal length when GhBPE is overexpressed. Further, the joint response to JA and GA of GhBPE and GhPRGL, together with their complementary expression profiles in the early stage of petal growth, suggests a novel GhBPE-GhPRGL module that controls the size of ray petals. GhPRGL promotes ray petal elongation in its early stage especially, while GhBPE inhibits ray petal elongation particularly in the late stage by inhibiting the expression of GhPRGL. JA and GA operate in concert to regulate the expression of GhBPE and GhPRGL genes, providing a regulatory mechanism by which ray petals could grow to a fixed length in gerbera species.

A GASA Protein Family Gene, CmGEG, Inhibits Petal Growth in Chrysanthemum

“…In order to investigate whether the alteration in petal length was attributed to cell elongation or cell division, we conducted measurements of the size and number of epidermal cells in three distinct regions of the petal (top, middle, and basal) from CmGEG-OE, CmGEG-VIGS, and mock samples after a 6-day cultivation period, following the methodology outlined by Jiang et al [ 48 ] ( Figure 5 A). As shown in Figure 5 B,C, the length of the epidermal cells in the top, middle, and basal regions of the CmGEG-OE petals was significantly shorter than those in the mock.…”

“…Protoplasts containing the pCAMBIA1301-CmGEG-GFP fusion plasmid and the pCAMBIA1301-GFP empty vector were extracted from the leaves of 4-week-old Arabidopsis plants, following the previously established protocol [ 48 , 75 ]. To label the cell membrane, the cell membrane localization marker mCherry (a plasmid with the cell membrane localization signal fused to the mCherry protein) was co-transfected into the Arabidopsis protoplasts.…”

“…The petals were isolated from the inflorescence, submerged in sterile water, wrapped in gauze, and then subjected to different A. tumefaciens infiltration solutions under a vacuum of −0.09 MPa for 10 min, followed by a gradual return to normal atmospheric pressure within 2 min, following the procedures outlined in previous studies [ 14 , 48 ]. Subsequently, the infiltrated petals were rinsed with sterile distilled water (ddH 2 O) and placed in culture dishes lined with filter papers.…”

“…Notably, Gibberellic-Acid-Stimulated Like-1 ( ZmGSL-1 ) is associated with lateral root development in maize, while silencing Snakin-1 in potato leads to plant dwarfing, a reduced leaf size, and significant alterations in leaf shape [ 44 , 45 ]. Additionally, GEG (the Gerbera hybrida homolog of the gibberellin [GA]-stimulated transcript 1 [ GAST1 ] from tomato) has been identified as an inhibitor during the later stage of ray petal growth, whereas GhPRGL promotes ray petal elongation in the early stage [ 46 , 47 , 48 ]. However, research on the involvement of GASA s in the growth and development of Asteraceae remains limited.…”